How to model and blend same like the image
I would do it with some bevels:


Create a cube. Mirror it on the X and Z axis.





Inset the front face with i and b for boundary. Pull it on the Y axis and extrude it.






Select the angle edges, and ctrlB to bevel.






Slide the new edges with GG so decrease the roundness on the back block angles.





Inset faces, add edge loops to sharp the angles...